Catalyst for preparation of polybutadiene

ABSTRACT

1,3-Butadiene is polymerized employing a four-component catalyst comprising: a) an organoaluminum hydride; b) an organolithium or organosodium compound; c) a titanium halide compound; and d) an ether.

This application is a division of copending application Ser. No.463,978, filed Apr. 25, 1974 U.S. Pat. No. 3,896,102.

BACKGROUND

The invention relates to a method and a catalyst for polymerizing1,3-butadiene. In another aspect it relates to a method and a catalystfor the production of trans-polybutadiene.

It is known that polymers of dienes, such as 1,3-butadiene, are veryuseful polymeric materials. Polybutadiene is produced with multifariousproperties, many of which can be determined by the polymerizationprocess and/or catalyst. For example, catalysts can be chosen to produceeither a cis or trans polybutadiene, and in general, the higher thetrans content of polybutadiene the more resinous it is. High transpolybutadiene is an elastic, tough, crystalline, thermoplastic solidwhereas a high cis polybutadiene is a rubbery material. Although thereare a number of processes and catalysts known for polymerizing1,3-butadiene, there is still a demand for new catalysts and processeswhich are useful to polymerize 1,3-butadiene.

It is an object of the invention to produce polymers.

Another object of the invention is to produce polymers of 1,3-butadiene.

Another object of the invention is to produce trans polybutadiene.

Still another object of the invention is to provide a novel catalyst forthe production of polybutadiene.

Other objects, aspects, and advantages of the invention will becomeapparent to those skilled in the art upon studying the specification andthe appended claims.

SUMMARY

In accordance with the invention a polybutadiene is produced bycontacting 1,3-butadiene under polymerization conditions with a novelcatalyst comprising: a) an organoaluminum hydride; b) an organolithiumor organosodium compound; c) a titanium halide component; and d) anether.

DETAILED DESCRIPTION OF THE INVENTION

The organoaluminum hydride employed in the catalyst system of thepresent invention is represented by the general formula R_(a) AlH_(b)wherein R is an alkyl, cycloalkyl, and combinations thereof, such asalkylcycloalkyl, containing from about 1 to 16 carbon atoms, a is aninteger from 1 to 2, b is an integer from 1 to 2 such that the sum of aplus b equals 3. Examples of such organoaluminum hydrides includedimethylaluminum hydride, diethylaluminum hydride, ethylaluminumdihydride, methyl isopropylaluminum hydride, cyclohexylaluminumdihydride, ethyl cyclohexylaluminum hydride, methyl4-ethylcyclohexylaluminum hydride, didodecylaluminum hydride, ethylhexadecylaluminum hydride, and eicosylaluminum dihydride.

The organolithium or organosodium compound suitable for use inaccordance with the invention is represented by the general formulaR'M_(x) wherein x is an integer from 1 to 4, R' is a hydrocarbon radicalselected from the group consisting of aliphatic and cycloaliphaticradicals containing from 1 to about 20 carbon atoms per radical and M islithium or sodium. Examples of suitable organolithium and/ororganosodium compounds include methyllithium, isopropyllithium,n-butyllithium, t-octylsodium, n-decylsodium, 4-phenylbutyllithium,cyclohexyllithium, 4-butylcyclohexylsodium, 4-cyclohexylbutyllithium,dilithiomethane, 1,4-disodiobutane, 1,10-dilithiodecane,1,20-dilithioeicosane, 1,4-disodiocyclohexane, 1,4-disodio-2-butene,1,8-dilithio-3-decene, 1,2-dilithio-1,2-diphenylethane, and1,2-disodio-1,8-diphenyloctane.

The titanium halide component of the catalyst system is selected fromthe group consisting of titanium tetrachloride and molecular iodine,titanium tetrabromide and molecular iodine, or titanium tetraiodide withor without molecular iodine.

The ethers suitable for use in the invention are represented by thegeneral formula R"-O-R'" wherein R" and R' " are alkyls or cycloalkylscontaining from about 1 to 12 carbon atoms per R" or R'" group andwherein the ether contains up to 20 carbon atoms per molecule.Nonlimiting examples include dimethyl ether, diethyl ether, di-n-butylether, methyl ethyl ether, methyl dodecyl ether, ethyl cyclohexyl ether,dicyclohexyl ether, n-octyl n-dodecyl ether, and mixtures thereof.

The catalyst composition, on a mole ratio basis, varies widely.Generally, the mole ratio of the organolithium or organosodium compoundto the organoaluminum hydride is in the range of from about 1:1 to 1:3,although good results were obtained employing a mole ratio ranging fromabout 1:1 to 1:1.5. The mole ratio of the titanium tetrahalide in thetitanium halide component of the catalyst to the organoaluminum hydrideis in the range of from about 1:1 to 0.1:1, although good results wereobtained with a mole ratio ranging from about 0.5:1 to 0.2:1. The moleratio of titanium tetrachloride or titanium tetrabromide to themolecular iodine is in the range of from about 1:1 to 0.1:1, but goodresults were obtained employing a mole ratio ranging from about 0.5:1 to0.33:1.

With respect to the quantity of ether employed in the catalyst system,the amount varies widely and depends upon the choice of ether and to alesser degree upon the relative importance of conversion versus transcontent of the polymer. Although many ethers are suitable for use in theinvention, methyl ethers have the greatest effectiveness per unitweight. Also initially increasing the amount of ether increases both theconversion and trans content; however, generally a point is reachedbeyond which additional ether will increase trans content but reduceconversion. Normally, though, the amount of ether present during thepolymerization is in the range of from about 0.01 to 30 parts by weightper hundred parts by weight butadiene.

Generally, the polymerization mixture contains a diluent. Diluentssuitable for use in the process are compounds which are not detrimentalto the polymerization process. Suitable diluents include paraffinic andcycloparaffinic hydrocarbons and mixtures thereof. Examples of suchdiluents include n-hexane, n-heptane, 2,2,4-trimethylpentane, andcyclohexane. The inventive process is operable over a broad range ofconcentrations of butadiene in the diluent. For example, normally theconcentration of butadiene in the diluent is in the range of from about1 to 200 weight percent, but a range of from about 5 to 50 weightpercent has been used successfully.

The total quantity of catalyst required to effect polymerization of the1,3-butadiene to polymer can be determined readily by one skilled in theart and depends upon the trans content desired and the particularconditions such as temperature, impurities, molecular weight desired andthe like. Normally, the total quantity of catalyst expressed in grammillimoles of the organoaluminum hydride per hundred grams of butadienevaries in the range of from about 0.3 to 30; however, a more economicalrange of from about 0.5 to 10 has produced good results.

The tran content of the polymer produced employing the inventivecatalyst system varies considerably. Normally the polymer produced has asubstantial trans content, such as for example, between 60 to 95percent; however, a polymer with a trans content outside this range canbe made with the present catalyst system.

Polymerization can take place in a wide range of temperature. Aconvenient range in which effective polymerization can be obtained is 0°to 120° C, with good results obtained employing a range from about 30°to 80° C. Also the polymerization pressure varies widely. Thepolymerization reaction can be carried out under autogeneous pressure orat any suitable pressure sufficient to maintain the reaction mixturesubstantially in the liquid phase. Generally the pressure will thusdepend upon the particular diluent being employed and the temperature atwhich the polymerization is carried out. However, higher pressures canbe employed if desired by using a suitable method such as thepressurization of the reactor with the gas which is inert with respectto the polymerization reaction.

Various materials are known to be detrimental to the catalyst of theinvention. These materials include carbon dioxide, oxygen, and water. Itis usually desirable, therefore, that the reactants and catalysts befreed of these materials as well as other materials which may tend toinactivate the catalyst. Furthermore, it is desirable to remove air andmoisture from the reaction vessel in which the polymerization is to beconducted. Upon completion of the polymerization, the polymerizationmixture is then treated to inactivate the catalyst and to recover thepolymer. A suitable method for accomplishing this result involves steamstripping the diluent from the polymer. In another suitable method acatalyst-inactivating material, such as an alcohol, is added to themixture so as to inactivate the catalyst and cause precipitation of thepolymer. The polymer is then separated from the alcohol and diluent byany suitable means, such as decantation or filtration. It has been foundto be advantageous to add an antioxidant, such as2,6-di-t-butyl-4-methylphenol to the polymer solution prior to recoveryof the polymer.

Polymers can be compounded by methods as known in the art. Compoundingingredients, such as fillers, dyes, pigments, curing or crosslinkingagents, softeners, reinforcing agents, and the like, can be used in thecompounding operation. In manufacturing finished articles, the polymercan be molded or extruded. They can be advantageously employed in themanufacture of items such as insulating wires and cables, including suchfor underwater service, battery cases, and golf ball covers.

ILLUSTRATIVE EXAMPLES

The polymerizations were carried out under nitrogen in capped beveragebottles employing anhydrous reactants and conditions. The bottles weretumbled in a constant temperature bath for the stipulated polymerizationtimes and at the stipulated temperatures. Following polymerization,2,6-di-t-butyl-4-methylphenol (1 part by weight per hundred parts ofmonomer) was added in a 50/50 volume toluene/isopropyl alcohol solution,the polymer solutions were filtered, and the polymers were coagulated byadding the filtrates to isopropyl alcohol. The polymers were thencollected by filtration and dried at reduced pressure. Polymers thusproduced were thermoplastic in character.

Shown immediately below are definitions of abbreviations and termsemployed in the following working examples. Also included aredescriptions and references for analytical and evaluation methodsemployed.

m.p. -- Melting point, ° C;

f.p. -- Freezing point, ° C;

mhm. -- Gram millimoles per hundred grams monomer;

phm. -- Parts by weight per 100 parts by weight monomer.

a. Inherent Viscosity (I.V.) was determined using tetrahydrofuraninstead of toluene by the process shown in U.S. Pat. No. 3,278,508,column 20, note a, with the further modification that the solution wasnot filtered through a sulfur absorption tube, but rather a sample ofthe solution was filtered through a fritted glass filter stick of gradeC porosity and pressured directly into the viscometer.

b. Differential Thermal Analysis (DTA) melting points and freezingpoints were determined on DuPont instrument DTA-900 differential thermalanalyzer employing a differential scanning calorimeter cell. The pointof maximum deflection of the endotherm or exotherm under a nitrogenatmosphere was observed. Heating and cooling rates employed were each10° per minute. The size of samples analyzed was approximately 15 mg.

c. Polymer microstructure, i.e., trans and vinyl contents weredetermined by infrared absorption spectoscopy (I.A.S.).

EXAMPLE I (Runs 1-18)

The following inventive runs illustrate the invention and, inparticular, the effect on conversion and trans content of varying theamount of ether, i.e., dimethyl ether, employed. Also the amount of theother catalyst components was also varied but at constant relativeamounts. The runs were made in accordance with the following recipe andthe results are tabulated below.

                  Recipe                                                          ______________________________________                                                               phm                                                    n-Hexane               660                                                    n-Butyllithium (n-BuLi)                                                                              variable                                               Diethylaluminum hydride                                                        (Et.sub.2 AlH)        variable                                               Dimethyl Ether (Me.sub.2 O)                                                                          variable                                               Iodine                 variable                                               Titanium tetrachloride variable                                               Butadiene              100                                                    Temperature (° C)                                                                              50                                                    Time (Hours)            3.66                                                  ______________________________________                                    

                                      TABLE I                                     __________________________________________________________________________                           Con-                                                   Run                                                                              n-BuLi                                                                            Et.sub.2 AlH                                                                      TiCl.sub.4                                                                        Iodine                                                                            Me.sub.2 O                                                                        version                                                                           DTA   Trans                                                                             Vinyl                                    No.                                                                              mhm mhm mhm mhm mhm Wt. %                                                                             m.p.                                                                             f.p.                                                                             Wt %                                                                              Wt. %                                                                             IV                                   __________________________________________________________________________     1 1.8 1.8 0.5 1.0 0   58  -- --  3.3                                                                              5.1 3.15                                  2 1.8 1.8 0.5 1.0 2   61  -- -- 16.9                                                                              4.9 1.34                                  3 1.8 1.8 0.5 1.0 4   70  -- -- 51.0                                                                              3.5 2.85                                  4 1.8 1.8 0.5 1.0 8   74  -- -- 75.7                                                                              2.7 3.24                                  5 1.8 1.8 0.5 1.0 16  52   90                                                                              54 86.2                                                                              2.3 3.87                                  6 1.8 1.8 0.5 1.0 32  16  110                                                                              80 85.9                                                                              2.1 1.94                                  7 2.7 2.7 0.75                                                                              1.5 0    5  -- -- --  --  --                                    8 2.7 2.7 0.75                                                                              1.5 2   26  -- -- --  --  --                                    9 2.7 2.7 0.75                                                                              1.5 4   62  -- -- 41.9                                                                              4.0 2.33                                 10 2.7 2.7 0.75                                                                              1.5 8   72  -- -- 75.3                                                                              2.8 2.53                                 11 2.7 2.7 0.75                                                                              1.5 16  70  -- -- 87.4                                                                              2.3 2.52                                 12 2.7 2.7 0.75                                                                              1.5 32  30  108                                                                              81 88.2                                                                              2.1 2.19                                 13 3.6 3.6 1.0 2.0 0    0  -- -- --  --  --                                   14 3.6 3.6 1.0 2.0 2    0  -- -- --  --  --                                   15 3.6 3.6 1.0 2.0 4   64  -- -- 31.3                                                                              4.4 2.04                                 16 3.6 3.6 1.0 2.0 8   67  -- -- --  --  --                                   17 3.6 3.6 1.0 2.0 16  68  -- -- 83.4                                                                              2.4 3.27                                 18 3.6 3.6 1.0 2.0 32  18  109                                                                              81 --  --  --                                   __________________________________________________________________________

Generally trans values were increased by increasing the dimethyl etherlevel. Since DTA data is relatively more dependable than trans valuesdetermined by IAS, an examination of the DTA data and a comparison ofthe relationship between DTA data and trans values indicates the transvalue for run 6 is erroneously low. Also the polymerization rate waspromoted by adding additional dimethyl ether up to a point beyond whichadditional ether suppressed the rate.

The inherent viscosity values of the polymers produced in accordancewith the invention indicated the polymers were of useful molecularweights.

EXAMPLE II (Runs 19-30)

The following runs illustrate the effects of variations in the solventwherein such variations were studied at various dimethyl ether levels.The runs were made in accordance with the following recipe and theresults are tabulated below.

                  Recipe                                                          ______________________________________                                                         phm                                                          n-Hexane, or cyclohexane,                                                      or toluene      660, 780, or 860 (respectively)                              n-Butyllithium   1.8 mhm                                                      Diethylaluminum hydride                                                                        1.8 mhm                                                      Dimethyl ether   variable                                                     Iodine           1.0 mhm                                                      Titanium tetrachloride                                                                         0.5 mhm                                                      Butadiene        100                                                          Temperature, ° C                                                                        50                                                           Time, hours      4                                                            ______________________________________                                    

                                      TABLE II                                    __________________________________________________________________________                    Con-                                                          Run       (CH.sub.3).sub.2 O                                                                  version                                                                           Trans                                                                             Vinyl  DTA                                             No.                                                                             Solvent                                                                              mhm   Wt. %                                                                             Wt. %                                                                             Wt. %                                                                             IV m.p.                                                                             f.p.                                        __________________________________________________________________________    19 n-Hexane                                                                             2     55  24.0                                                                              4.6 1.87                                              20 n-Hexane                                                                             4     55  --  --  --                                                21 n-Hexane                                                                             8     54  75.0                                                                              2.7 3.71                                              22 n-Hexane                                                                             16    32  --  --  -- 53 44                                          23 Cyclohexane                                                                          2     74  17.3                                                                              4.7 1.87                                              24 Cyclohexane                                                                          4     73  52.5                                                                              3.5 2.17                                              25 Cyclohexane                                                                          8     77  --  --  --                                                26 Cyclohexane                                                                          16    72  86.9                                                                              2.3 3.61                                                                             54 50                                          27 Toluene                                                                              2     69  15.7                                                                              3.9 4.82                                              28 Toluene                                                                              4     4   --  --  --                                                29 Toluene                                                                              8     0   --  --  --                                                30 Toluene                                                                              16    7                                                             __________________________________________________________________________

Aliphatic and cycloaliphatic diluents are clearly preferred overaromatic solvents as illustrated by the examples above.

EXAMPLE III (Runs 31-35)

The following runs illustrate the invention employing diethyl ether. Theruns were made in accordance with the following recipe and the resultsare tabulated below.

                  Recipe                                                          ______________________________________                                                               phm                                                    n-Hexane               660                                                    Diethylaluminum hydride                                                                              1.8 mhm                                                sec-Butyllithium       1.8 mhm                                                Diethyl ether          variable                                               Iodine                 0.8 mhm                                                Titanium tetrachloride 0.4 mhm                                                Butadiene              100                                                    Temperature, ° C                                                                              50                                                     Time, hours            18                                                     ______________________________________                                    

                  TABLE III                                                       ______________________________________                                        Run  (C.sub.2 H.sub.5).sub.2 O                                                               Conversion Trans  Vinyl                                        No.  phm       Wt. %      Wt. %  Wt. %  IV                                    ______________________________________                                        31   0.0       55          2.2   5.3    3.29                                  32   0.5       55         46.4   3.8    2.69                                  33   1.0       55         54.0   3.7    2.97                                  34   2.0       45         --     --     --                                    35   10.0      10         88.3   2.5    2.14                                  ______________________________________                                    

A very substantial increase in trans content was observed when thepolymerization mixture contained as little as 0.5 phm diethyl ether.Also the trans content was further increased by increasing the amount ofether; however, a point was reached whereby additional ether decreasedconversion.

EXAMPLE IV (Runs 36-39)

The runs shown below were made to determine the effect of varying theether level and the aluminum/titanium atom ratios. These runs were madein accordance with the following recipe and the results are tabulatedbelow.

                  Recipe                                                          ______________________________________                                                               phm                                                    n-Hexane               660                                                    Dimethyl ether         variable                                               Diethylaluminum hydride                                                                              1.8 mhm                                                n-Butyllithium         1.8 mhn                                                Iodine                 variable                                               Titanium tetrachloride variable                                               Butadiene              100                                                    Temperature, ° C                                                                              50                                                     Time, hours            4                                                      ______________________________________                                    

                                      TABLE V                                     __________________________________________________________________________                    Con-                                                          Run                                                                              TiCl.sub.4                                                                        Iodine                                                                            (CH.sub.3).sub.2 O                                                                 version                                                                           Trans                                                                             Vinyl   DTA                                           No.                                                                              mhm mhm mhm  Wt. %                                                                             Wt. %                                                                             Wt. %                                                                             IV  m.p.                                                                             f.p.                                       __________________________________________________________________________    36 0.4 0.8 5    38  90.6                                                                              2.2 3.61                                                                              99 70                                         37 0.6 1.2 0    46  23.4                                                                              5.1 1.21                                              38 0.6 1.2 1    56  25.3                                                                              1.8 2.24                                              39 0.6 1.2 5    11  89.4                                                                              2.2 2.87                                              __________________________________________________________________________

In a comparison of the conversion and trans content of run 36 with thatof runs 37 through 39, it is evident that the lower molar ratio ofaluminum alkyl hydride to titanium halide in the latter runs adverselyaffected the reaction.

EXAMPLE V (Runs 40-44)

The following runs illustrate the operation of the inventive system at70° C. The runs were made in accordance with the following recipe andthe results are tabulated below.

                  Recipe                                                          ______________________________________                                                               phm                                                    n-Hexane               660                                                    Dimethyl ether         variable                                               Diethylaluminum hydride                                                                              1.8 mhm                                                n-Butyllithium         1.8 mhm                                                Iodine                 variable                                               Titanium tetrachloride variable                                               Butadiene              100                                                    Temperature, ° C                                                                              70                                                     Time, hours            4                                                      ______________________________________                                    

                  TABLE VI                                                        ______________________________________                                                                   Conver-                                            Run  TiCl.sub.4                                                                           Iodine  (CH.sub.3).sub.2 O                                                                   sion   Trans Vinyl                                 No.  mhm    mhm     mhm    Wt. %  Wt. % Wt. % IV                              ______________________________________                                        40   0.45   0.9     2      37     66.6  3.6   2.52                            41   0.45   0.9     4      27     81.2  2.9   3.39                            42   0.45   0.9     6      53     86.9  2.7   2.82                            43   0.45   0.9     8      27     86.3  2.7   3.22                            44   0.5    1.0     8      53     87.7  2.6   3.07                            ______________________________________                                    

I claim:
 1. A catalyst for polymerizing 1,3-butadiene to produce transpolybutadiene comprising:a. an organoaluminum hydride represented by thegeneral formula R_(a) AlH_(b) wherein R is alkyl, cycloalkyl or mixturesthereof containing from about 1 to 16 carbon atoms, a is an integer from1 to 2, b is an integer from 1 to 2 such that the sum of a plus b equals3; b. an organolithium or organosodium compound represented by thegeneral formula R'M_(x) wherein x is an integer from 1 to 4, R' is ahydrocarbon radical selected from the group consisting of aliphatic andcycloaliphatic radicals containing from about 1 to 20 carbon atoms perradical and M is lithium or sodium; c. a titanium halide componentselected from the group consisting of titanium tetrachloride plusmolecular iodine, titanium tetrabromide plus molecular iodine, andtitanium tetraiodide; and d. an ether represented by the general formulaR"OR''' wherein R" and R''' are alkyl or cycloalkyl groups containingfrom about 1 to 12 carbon atoms per R" or R''' group and wherein theether contains up to 20 carbon atoms per molecule.
 2. The catalyst ofclaim 1 wherein the mole ratio of the organolithium or organosodiumcompound to the organoaluminum hydride is in the range of from about 1:1to 1:3; wherein the mole ratio of the titanium tetrahalide in thetitanium halide component to the organoaluminum hydride is in the rangeof from about 1:1 to 0.1:1; wherein the mole ratio of titaniumtetrachloride or titanium tetrabromide to molecular iodine is in therange of from about 1:1 to 0.1:1; and wherein the amount of the etherpresent during the polymerization is in the range of from about 0.01 to30 parts by weight per hundred parts by weight butadiene.
 3. Thecatalyst of claim 2 wherein the mole ratio of the organolithium ororganosodium compound to the organoaluminum hydride is in the range offrom about 1:1 to 1:1.5; wherein the mole ratio of the titaniumtetrahalide in the titanium halide component to the organoaluminumhydride is in the range of from about 0.5:1 to 0.2:1; wherein the moleratio of titanium tetrachloride or titanium tetrabromide to moleculariodine is in the range of from about 0.5:1 to 0.33:1.
 4. The catalyst ofclaim 3 wherein the organoaluminum compound is diethyl aluminum hydride,the organolithium compound is selected from the group consisting ofnormal or secondary butyllithium, the titanium halide component istitanium tetrachloride plus molecular iodine, and the ether is dimethylether.
 5. The catalyst of claim 1 wherein the trans content of the transpolybutadiene ranges from about 60 to about 95 weight percent.